The simian immunodeficiency virus of macaques (SIV), a lentivirus closely related to the human immunodeficiency viruses (HIV), induces an AIDS-like disease in juvenile rhesus monkeys. This virus and the rhesus monkey will be utilized as an experimental model for the study of AIDS. This model will be employed to: I. Characterize the SIV-specific cytolytic T lymphocyte response in SIV-infected rhesus monkeys. II. Assess the potential therapeutic utility of recombinant soluble CD4-toxin conjugates in SIV-infected rhesus monkeys.